public static long roadsAndLibraries(int n, int c_lib, int c_road, List<List<int>> cities)
    {
        if(n == 0) return 0;
        if(c_lib <= c_road) return n * (long)c_lib;
        
        var connections = new Dictionary<int, List<int>>();
        for(int c = 1; c <= n; c++)
        {
            connections[c] = new List<int>();
        }
        foreach(var cityPair in cities)
        {
            connections[cityPair[0]].Add(cityPair[1]);
            connections[cityPair[1]].Add(cityPair[0]);
        }
        
        var queue = new Queue<int>();
        var visited = new HashSet<int>();
        var cost = 0L;
        
        for(int c = 1; c <= n; c++)
        {
            if(visited.Contains(c))
            {
                continue;
            }
            
            cost += c_lib;
            queue.Enqueue(c);
            visited.Add(c);
            while(queue.Count > 0)
            {
                var city = queue.Dequeue();
                foreach(var neighbour in connections[city])
                {
                    if(!visited.Contains(neighbour))
                    {
                        queue.Enqueue(neighbour);
                        visited.Add(neighbour);
                        cost += c_road;
                    }
                }
            }
        }
        return cost;
    }